1. Field of the Invention
The present invention relates to explosion detection and suppression systems for detecting and preventing explosions in protected areas. More particularly, the invention relates to a rate of rise detector that accurately and reliably detects pressure increases in a protected area and then triggers explosion suppression equipment for preventing and/or inhibiting explosions in the protected area.
2. Description of the Prior Art
Explosion protection systems are commonly installed in industrial and commercial areas for preventing explosions in protected areas. These systems include a detector assembly that measures pressure increases in the protected area and then triggers explosion suppression equipment when the pressure rises at a rate above a threshold rate or reaches an absolute pressure level above a threshold pressure level.
Unfortunately, prior art detector assemblies often fail to quickly and reliably trigger their corresponding suppression equipment because of the manner in which they calculate pressure increases. Specifically, prior art detector assemblies determine the rate of pressure rise (dP/dt) in a protected area by sampling the pressure in the area at pre-determined time intervals and then determining the difference between the most recent pressure measurement and the immediate preceding pressure measurement. This difference is then divided by the time interval between the two pressure measurements, and the result is compared to a threshold rate. If the calculated rate exceeds the threshold rate, the detector assembly triggers the suppression equipment.
This method of determining the rate of pressure rise is slow and inaccurate for a number of reasons. First, momentary pressure variations and electromagnetic disturbances that occur within the protected areas often cause spikes in the measured pressure readings, thus resulting in inaccurate pressure rise calculations. To accommodate for these inaccurate readings and to prevent inadvertent triggering of the suppression equipment, prior art detector assemblies do not trigger their corresponding suppression equipment until several of the calculated rates have exceeded the threshold rate over an extended time period. Although this delay reduces the frequency of inadvertent triggering of the suppression equipment, it also delays the triggering of the suppression equipment when the pressure actually is rising at dangerous rates and therefore reduces the effectiveness of the suppression equipment.
Another related problem with prior art detector assemblies is that these same momentary pressure variations and electromagnetic disturbances also often cause monitored absolute pressure readings to exceed the absolute threshold level, again resulting in inadvertent triggering of the suppression equipment. As with the rate of rise pressure calculations, prior art detector assemblies accommodate for these inaccurate readings by delaying the triggering of the suppression equipment until the monitored absolute pressure readings exceed the absolute threshold level for a pre-determined time interval. Once again, this delays the triggering of the suppression equipment during actual explosive conditions.
Prior art detector assemblies are also limited because they are typically configured for use with a particular protected area and cannot be easily reconfigured for use in a different area having dissimilar operating characteristics. The threshold rates of prior art detector assemblies are also difficult to adjust without comprising the accuracy of the detectors.